Production of esters



' problems of the prior art and to-provide an. im-

1 carbon atom.'.

the invention a'rejdescribed. 1

ee a 12, 219451 momen F Estrnns Will'iam E.Hanfo1-d and John B. Roland, Wilnilngton, Del., a'slignors to E. I. du. Pont' (1e! Nemours & Company, Wilmington, D.el;, a cor-- porationof Delaware" Application September 19,1941, Serial No. 411,551;

iiolaims. (Cl. 260-488) A 3 1 Consideration of this equation shows that the invention relates esters containing a carbethoxy group linked to a tertiarycarbonatom and more specifically to ethyl alpha-methyl alphaeethylbuty'rate and to a. process for its v '7 preparation. l

A number of esters containing carbethoxy groups linked to tertiary carbon atoms are knownand their preparation has been successfully carried out by esteriflcation-of the corresponding acids. The esterification rates of such acids however are'impractically slow; and methods involv ing intermediate" steps are tedious and, expen- I sive.-, It is an object of this invention to overcome the proved process forthe production of esters containing a carbethoxygroup linked to a tertiary The strong acid used as catalyst may be any ethylene should be in molar excess. Preferably, the mole ratio of ethylene to carbon monoxide should lie between 1:1'and 6:1, although wider variations are permissible.

. of the acid-reacting hydrates of inorganic com- ZDCI JHaOM, TiCl4.(H2O) and the like. subscript :c in the foregoing formulas may vary pounds. Suitable examples ofsuch substances are BFaKHzO) a, SO3.(H) z, P205.(3H20)z, The

g from 0.5 to about 5. Boron fluoride hydrate with It is a further and morespecific object ofthis invention to provide a process forproducing ethyl alpha-methyl-alpha-ethylbutyrate.

Other objectsland' advantages of this invention will be apparent in the following specification in which the details and preferred embodiments .of

Accordingtothe present invention ethyl alphavmethyl-alpha ethylbutyrate is prepared'by heating a mixture of carbon monoxide and ethylene in'afstrong'ly acid medium. 1 As it is generally p'racticed,the present invention comprises heat ing at a'temperature within the range of 50 to 200 C. a mixture of carbon monoxide, ethylene and a strong acid catalyst, the reactants being vmaintained in intimate mutual contact such asby agitation, turbulent flow, eflicient bubbling of the gases through the liquidphase or the like; l The heating is preferably carried out at a temperature within the range offrom 75 to 150 0,, although higher :or lower temperatures may be 1 used. However, lower temperatures tend-to favor a slow'reaction rate and higher temperatures makefor diflicult control'of the reaction as well as the introduction of. numerous side reactions.

Inorder to maintain asuflicient concentration of carbon monoxide and ethylene the reaction is suitably carried out under pressure. This may be a mole ratio of BFa to water from 1:1 to 1:3 is a preferred catalyst.

The yield'of ethyl alpha-methyl-alpha-an butyrate is considerably improved by the inclusion of a peroxide compound in the reaction charge. By peroxidecompounds it is meant to include compounds which are either formed by the action of hydrogen peroxide on ordinary acids or else give rise to hydrogen peroxide on treatment with dilute sulfuric acid, Benzoyl peroxide,

' acetyl peroxide, acetyl benzoyl peroxide, alkali metal and ammonium persulfated typify types of peroxides which are advantageous in the operation of this process.

The following general procedure illustrates one manner of practicing this invention which may be operated as a batch, semi-batch or continuous process. A'reaction vessel is charged .with boron fluoride hydrate and if desired a small amount of peroxide catalyst. The vessel is closed and placed inan agitating machine fitted with a heating coil. Internal, recording and external controlling thermocouples are placed in position and the vessel is connected to a source of ethylene. Ethylene is admitted to the. vessel to such a pressure that, with the additional pressure of carbon monoxide, the pressure at reaction temperature will be safely within the limits of the vessel. The vessel is thenclosed off from the f ethylene supply, disconnected and connected to asourceof carbon monoxide. The carbon monoxideis admitted to the desired extent and heating and agitation are started. Alternatively the carbonmonoxide may be introduced first or the as low as oneatmosphere total gas pressure,'ibut is preferably in the range of from'.200 t0'1000 atmospheres. The upper limit of pressure which may be used is determined of theequlpmentavailable. v

The overall equation for the reaction is g 4o.H.+1H,o+1oo-$o1z,+$-coocm.. v

solely by the. strength two gases may be premixed in the desired proportions and then charged into the reactor. 7

Upon reaching the reaction temperature the reaction starts and maybe followed by a. pressure decrease. v The pressure may be maintained in the desired range during the reaction by the periodic'; additionof gas, preferably ethylene. When the reaction is complete as evidenced by cessation of pressure drop the vessel is allowed to cool,

bled of excess g'as,"opened and'discharg'ed. The

ethyl I alpha-methyl-alpha-ethylbutyrate is isolated from the reaction mixture by fractional distillation or by steam distillation followed by fractional distillation of the organic phase of the steam distillate.

Pure ethyl alpha-methyl-alpha-ethylbutyrate boils at 166-166.? C. at atmospheric pressure and has n =1.4100, 014 0.8687. The ester has a decidedly pleasant camphoraceous odor. This ester, which is decidedly resistant to alkali treat-- ment, may be identified by hydrolysis with 48% hydrobromic acid. The ethyl bromide evolved from this hydrolysis is collected and identified by its boiling point of 37-40 0., its refractive index at 265 C. of 1.4137 and by its insolubility in cold concentrated sulfuric acid. This other product of the hydrobromic acid hydrolysis is alphamethyl-alpha-ethylbutyric acid which may be converted by way of the chloride to the amide and anilide, compounds reported in the literature (Hardy, J. Chem. Soc. 1938, 464). The melting points of these derivatives of the product of the present invention are compared with Hardys derivatives in the table below:

1 Mixed Hardy's rz-M a-E Present Hardy s u butyrate products sample 23%;?

Degrees Degrees Degrees Degrees Amide 73-74 74-75 7445.5 75. 5-76 Anillde 87-88 84-35 85-86 87-87. 5

The following examples serve to illustrate the process of this invention and to demonstrate suitable conditions of operation. The quantities given are in parts by weight unless otherwise specified.

Example I agitation are started and during a reaction time of 10.75 hours throughout which the temperature is maintained at 114-115- C. and the pressure at 550-990 atmospheres the total observed pressure drop is 985 atmospheres. During the reaction the pressure is maintained in a desired range by the periodic addition of carbon monoxide. The vessel is cooled, bled of excess gas, opened and the reaction mixture discharged. This is steam distilled, the organic layer separated from the distillate and submitted to fractional distillation. After several small low boiling fractions the chief portion, amounting to 48 parts, is found to boil at 163-46 C. Analytical figures on this fraction are not entirely satisfactory and it is therefore submitted to precision distillation in a highly efficient, still. Pure ethyl alpha-methyl-alphaethylbutyrate of boiling point 166-4667 C. and refractive index 1.4100 is obtained. This sample analyzes 68.53% carbon and 10.61% hydrogen. The theoretical values of ethyl alpha-methylalpha-ethylbutyrate are 68.8% carbon and 10.38% hydrogen. r

Example II The preceding experiment is repeated except that ethylene is admitted to 400 atmospheres pressurefollowed by admission of carbon mon previously pointed out.

gThe total pressure of ethylene and carbon monoxide in the operation of, this process may be as low as about one atmosphere but is prefer ably higher, for example, from about200 atmospheres to about 1000 atmospheres. The ratio of ethylene to' carbon monoxide as measured by pressure) may range from about 1:3

to 10:1 or more. In general practice it is'preferable however to keep the ratio between about 1:1 and 6:1.

The ethylene used in this invention should be of good'quallty. It may however contain small, amounts of ethane, methane, hydrogen, nitrogen,

'carbon dioxide or oxygen. The tolerable amount of these impurities varies with the nature-of the contaminant and is preferably kept low. Oxygen may have a corrosive action in this reaction system and its concentration is therefore kept as low as practical. The other gases such as nitrogen have no deleterious. effect on the reaction and may in some instances be desirable. For example, if agitation is effected by bubbling the carbon monoxide and ethylene through the liquid phase, nitrogen' may be used to advantage to increase the efficiency of this agitation.

The carbon monoxide used may be obtained from various commercial sources such as, for example, from water gas, producer gas, coke oven gas and the like. In order to obtain products of the highest purity it is preferable to remove ethylene in a strongly acid medium, the ethylene from such commercial gases objectionable constituents.

Ethyl alpha-methyl-alpha-ethy1butyrate is suitably used as a solvent for a number of plastics and oils and ismiscible. with representative organic solvents. Suitable examples of plastics dissolved in this ester (either hot or cold) are ethyl cellulose; copolymers of vinyl acetate and vinyl chloride; chlorinated polyvinyl chloride; phenolformaldehyde resins; polystyrene; polyisobutylene; polyethylene; acetals of polyvinyl alcohol and the like. The highchemical stability of the ester of this invention makes it particularly useful in many of these applications. Ethyl alpha-methyhalpha-ethylbutyrate also has a very pleasant, camphoraceous odor which is quite persistent in small quantities. This property makes the ester useful as an ingredient for perfumes and cosmetics.

Various changes may be departing therefrom or sacrificing any of the advantages thereof.

What is claimed is: 1. A process for the preparation of ethyl alphamethyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and being present in molar excess, said strong acid Thisv reaction 9 There .is obtained from p c..- although preferably from about '75 to C. as

made in the details and preferredembodiments'of this invention without methyl-alpha-ethylbutyrate being an acid-reacting hydrate of an inorganic compound.

' 2. A process for the preparationof ethyl alphamethyl-alpha-ethylbutyrate which heating a mixture of carbon monoxide and ethylene in the presence of a strong acid catalyst, the reactants being maintained in intimate mutual contact and the ethylene being present in molar excess, said strong acidbeing an acid-reacting hydrate of an inorganic compound.

3. A process for the preparation of ethyl alphamethyl-alpha-ethylbutyrate which comprises heating a 'mixture of carbon monoxide and ethylene at a temperature in the range of 50 to 200 C., in the presence of a strong acid catalyst, the reactants being maintained in intimate mutual contact and the ethylene being present in molar excess, said strong acid being an acidreacting hydrate of an inorganic compound.

4. A process for the preparation of ethyl alphamethyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene at a temperature in the range of 75 to 150 C., in the presence of a strong acid catalyst, the reactants being maintained in intimate mutual contact and the ethylene being'presentin a molar excess, said strong acid being an acid-reactin hydrate of an inorganic compound. a

5. A process for the preparation of ethyl alphawhich comprises heating a mixture of carbon monoxide and ethylene at a temperature in the range of 50.

to 200 C. and at a pressure of 200- to 1000 atmospheres, in the presence of a strong acid catalyst, the reactants being maintained in intimate mutual contact and the ethylene being present in molar excess, said strong acidbeing an acidreacting hydrate of an inorganic compound.

6. A process for the preparation of ethyl alphamethyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene in the presence of a strong acid catalyst and a peroxide compound, at a temperature in the range of 50 to 200 C. and at a pressure of at least one atmosphere, the ratio of ethylene to carbon monoxide being in the range of from above 1 to 1 to as high as to 1, said strong acid being an acid-reacting hydrate of an inorganic compound.

7. A process for the preparation of ethyl alphamethyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene in the presence of boron'fluoride' hydrate and the ethylene beingpresent in molar excess.

8. A process for the preparation of ethyl alpha.

comprises methyl-alpha-ethylbutyrate which comprises heating a'mixtur'e of carbon monoxide and ethylene at a temperature in the range of 50 to 200 C. and at a pressure 01' at least one atmosphere, in the presence of boron fluoride hydrate, the reactants being maintained in intimate mutual contact and the ethylene being present in molar excess. g

9. A process for the preparation of ethyl alphamethyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene in the presence of boron fluoride hydrate and a peroxide compound, at a temperature in the range of 50 to 200 C., and at a pressure of at least one atmosphere, the ratioof ethylene to carbon monoxide being in the range of from above 1 to 1 to as high as 10 to 1.

10. A process for the preparation of ethyl alpha-methyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene at a temperature in the range of to C., in the presenc of boron fluoride hydrate, the reactants being maintained in intimate mutual contact and the ethylene being present inmolar excess.

11. .A process for the preparation of ethyl alpha-methyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene in the presence of boron fluoride hydrate and a peroxide, at a temperature in the range of '75 to 150 C., and at a pressure of at least one atmosphere, the ratioof ethylene to carbon monoxide being in the range of from above '1 to 1 .to as high as 10 to 1.

12. A process for the preparation of ethyl alpha-meth'yl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene'at a temperature in the range of 75 to 150 C. and at a pressure of 200 to 1000 atmospheres, in the presence of a peroxide compound and boron fluoride hydrate, the reactants being maintained in intimate mutual contact and the ethylene being present in molar excess.

13. A process for the preparation of ethyl alpha-methyl-alpha-ethylbutyrate which comprises heating a mixture of carbon monoxide and ethylene in the presence of boron fluoride hydrate and a peroxide compound, at a temperature in the range of 75 to 150 C. and at a pressure of 200 to 1000 atmospheres, the ratio of ethylene to carbon monoxide being in the range of from above 1 to 1 to as high as 10 to 1.

- 14. Ethyl alpha-methyl-alpha-ethylbutyrate.

WILLIAM E. HANFORD.

JOHN R. ROLAND. 

